Piezoelectric ceramic materials are used in sensors, transducers, and actuators to convert energy between mechanical and electrical forms. Searching for ferroelectric ceramics with a higher Curie temperature has been a continuous task in the field of electroceramics due to the demand from high temperature piezoelectric applications.1, 2 The previous work reported in the literature was primarily focused on binary solid solution systems between two perovskite compounds,2-4 such as BiScO3—PbTiO3,5, 6 Bi(Mg1/2Ti1/2) O3—PbTiO37, 8 and BiInO3—PbTiO3.9, 10 In these binary systems, the dielectric and piezoelectric performances were observed to peak at the morphotropic phase boundary (MPB) composition where a composition-induced phase transition occurs.11 The MPB composition, usually a very narrow composition range, displays a specific Curie temperature in the binary solid solution.
The BiFeO3—PbTiO3 (BF-PT) binary system exhibits a high Curie temperature (630° C.) and a large tetragonality at the MPB composition and has been investigated for high-temperature piezoelectric applications.12-15 However, the high leakage current makes it difficult to pole the ceramic and the high coercive field leads to unsaturated hysteresis loops even at very high electric fields.15-17 In the mean time, the well-known PbZrO3—PbTiO3 (PZT) ceramics have demonstrated excellent dielectric and piezoelectric performances but the Curie temperature at the MPB composition (380° C.) is low for some applications.2, 11 As a result of the relatively low Curie temperature, use of PZT-based devices has been restricted.